On 08/08/12 21:14, Nikita Popov wrote:
On Fri, Jul 27, 2012 at 8:09 PM, Nikita Popov <nikita....@gmail.com> wrote:
5. Are multiple yields allowed? I.e. the rfc mentions something like
yield yield $a - what that would mean? I'd allow yield only be applied
to variable expression (lval) because double yield doesn't make sense to
me, but maybe I miss something.
yield yield $a would basically first yield $a and then receive some
value (via send) and yield that value again. Nothing you'd normally do
;) It was mentioned only as a syntax ambiguity consideration.
Actually I added some additional parenthesis requirements for yield.
For example you'd have to write the above as `yield (yield $a)` now
(which should be slightly more clear). I haven't yet reflected this
change in the RFC, but I'll add a section on it later.
6. “Sending values” section seems to be missing. Especially useful would
be to cover what happens with keys there and what is the syntax there -
is it just "$a = yield;"? Or does it mean when yield is used in
expression it becomes incoming yield? And, last but not least - do we
need sending into generators at all?
Yeah, I haven't written that section yet. But it is fairly simple: If
you go $generator->send($foo) then $foo will be the result of the
current `yield` expression. And yes, this also works with keys and
values. All of the following are valid:
$data = yield;
$data = (yield $value);
$data = (yield $key => $value);
The first case is the most common though. I.e. you usually use it
either as a generator or a reverse generator, not both. But doing both
is also common for cooperative multitasking etc.
Regarding the last question: I think the feature is worth adding. It
is a very powerful concept that is hard to implement otherwise. Useful
in particular for things like parsing and multitasking.
6. What happens if you send into a by-ref generator? Is the data sent
by-ref then? What if it's an expression that can't be send by-ref?
No, sending is always by-value. By-ref only affects the yielding part.
I now added the mentioned sections:
https://wiki.php.net/rfc/generators#yield_keyword
https://wiki.php.net/rfc/generators#sending_values
I also added a list of error conditions:
https://wiki.php.net/rfc/generators#error_conditions
Sorry for the delay,
Nikita
Hi Nikita,
I notice you require brackets round yield $k => $v and yield $v. Is this
the formal syntax, i.e. '(' T_YIELD var => var ')'? If so it makes sense
in a way, but it feels a little hackish. Does yield $v cause some sort
of parsing issue that putting it in brackets solves? I realise that it's
less ambiguous, but I don't like the idea of it. PHP's syntax has enough
special cases already IMO.
Regards,
--
Andrew Faulds
http://ajf.me/
--
PHP Internals - PHP Runtime Development Mailing List
To unsubscribe, visit: http://www.php.net/unsub.php
